Induction heating device



y 1943- E. s. GOODRIDGE Re. 22,322

INDUCTION HEATING DEVICE Original Filed April 19, 1941 YINVENTOR EDWARD S GOODRIDGE Reissued May 25, 1943 INDUCTION HEATING DEVICE Edward S. Goodridge. Port Washington, N. Y.. assignor to Induction Heating Corporation, New

York, N. Y., a corporation of New York Original. No. 2,308,240, dated January 12, 1943, Se-

rial No. 389,296, April 19, 1941. Application for reissue March 11, 1943, Serial No. 478,767

Claims.

This invention relates to heating arrangements and more particularly to furnaces of the high frequency induction type.

A principal object is to provide an improved induction furnace of the conveyor type.

Another object is to provide an improved construction and shape of field coil for induction furnaces generally. 7

Another feature relates to an induction furnace having a conveyor or movable platform for carrying a series of articles'through a magnetic induction field, the field beingproduced by a novel form of field coil whereby the articles can enter and exit from the field without employing a movable coil or flexible connections thereto.

A further feature relates to an improved form of field coil for high frequency induction heaters wherein the end sections of the coil are deflected out of the plane of the coil proper, to produce a predetermined initial and final "soak" or gradation at the beginning and ending of the heat treatment. f I

A further feature relates to a conveyor furnace of the high frequency induction type whereinthe articles are in a direction at an angle to the axis of the coil convolutions while allowing the articles to be surrounded. by the field within the convolutions without the necessity of employing a movable coil.

A still further feature relates to the novel organization, arrangement and relative disposition of parts which constitute an improved induction conveyor type furnace and an improved field coil therefor.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following details descriptions and the appended claims.

While the drawing is concerned primarily with the field coil in conjunction with the conveyor 01' a progressive heat treating furnace, only those parts are shown in detail which are necessary to an understanding of the invention. Furthermore, while the drawing illustrates one particular shape of elongated field 0011, it will be understood that the shape-may be varied to suit the configuration of the articles to be treated and to suit the distribution of the magnetic flux desired at various points during the progress of the article through the coil.- Accordingly, in the drawing which represents one of many forms which the invention may assume,

Fig. 1 is a top plan view of the field coil and conveyor unit embodying features of the invention.

Fig.1 is a front elevational view of Fig. 1.

Fig. 3 is a sectional view of Fig. 2, taken along the line 3-3 thereof and viewed in the direction of the arrows.

Fig. 4 shows a modification of Figs. 1-3.

Fig. 5 shows another modification of Figs. 1-3.

High frequency induction furnaces -may be roughly grouped into two categories, those wherein the article or charge moves along a line which is substantially parallel to the axis of the convolutions of the field coil, and those wherein the article or charge moves at an angle to the axis of the field coil. The first type is open to the objection that the conveyor as well as the charge must pass through the field coil, and if the conveyor or other support contains any conductive parts which are susceptible to the magnetic fiux, this reduces the heating emciency while unnecessarily heating such parts. The second type enables the field coil to be located in inductive relation to the charge while exerting negligible heating effect on the conveyor support: However, since in this second type of furnace the charge must be surrounded by the convolutions of the field coil, it is necessary to provide means to raise and lower the coil in order to make sure that the turns thereof enclose orsurround the charge. Heretofore, this has necessitated me chanical arrangements for-raising and lowering the coil and also the presence of flexible connections between the high frequency source of supply and the ends of the 0011. These mechanical connections are a source of diillculty and the flexible connections also tend to deteriorate and be moved to any considerabl distance.

eventually break. particularly where the coil must In accordance with this invention, it is possible to heat-treat articles by surrounding them with the inductive field while maintaining the coil stationary.

Referring to Fig. 1, there is shown a suitable 7 platform 2 so as to be carried thereby through the high frequency field. This field is produced by a convoluted coil the main body section I of 2 which issubstantially elongated andthe endsec flonslandlofwhicharebentoutoftheplane ofthebodysectioni asshownmore'clearlyin Figs. 2 and 3. Bythus bending theend sections of each convolution, it is possible to allow the article or charge to be moved in the direction of the arrow and the inclined characterlof the end sections enables the charge to enter the coil so that throughout the entire length of'the body section I, it is completely surroimded by the field end sections of the coil were in the same plane as the body section 3, it would be 11 to raise the coil in order to allow the article I to enter the new, and thereafter it would be necessary to lower the coil so as to bring the convolutions in. the proper coupling wittsrespect to the charge 8. Likewise, at the exit end of the coil, the end turns I are bent upwardly at a suilicient angle to enable the article or charge 8 to emerge from the field without changing the position of the coil. Preferably, the coil is made from metal tubing such as copper or the like which is adapted to be connected to a source of cooling medium such as cool air or water which can continually circulate through the coil as is well-known in the art. It will be understood of course that theterminals of the coil are connected by conductors I and l to any suitable source of high frequency current.

The deflected ends of the coil convolutions in addition to enabling the charge to enter and leave the field while maintaining the coil stationary,

also have the advantage that a graduated heating effect is produced at both the entrance and exit ends of the device. Thus as shown in Fig. 2

at the entrance end, the coupling between the charge 8 and the held of the coil is much less than the coupling existing therebetween when the charge is within the body section 3 and enveloped thereby. By proportioning the oil-setting or inclination of the end sections, it is possible therefore to graduate the heating eilect between any desired limits prior to subjecting the charge 5 to the maximum heating eil'ect of the main or body section l. Likewise, at the exit end by pro viding a predetermined offset to the end sections 5, it is possible to graduate the reduction in the heating eifect as the charge leaves the coil. It will be understood of course that the individual poles or convolutions of the coil are spaced apart from each other so as to prevent short-circuiting I of one or more complete turns of the coil. 1! the oases body portion 2, may be given any desired shape" in conformity with the shape of the article being treated. It will be understood of course, that while Figs. 1 and 2 show the coil disposed so that the axis of the convolutions is vertical, the coil may be located so that the said axis is horizontal or in any other angular position providing the end sections of each convolution are offset sufilciently to enable the charge or any projecting portion thereof to enter the coil while the latter is stationary.

Instead of employing a longitudinal conveyor and a straight-sided field coil, it will be understood that the invention can also be applied to rotating platform conveyors in which event the field coll instead of being straight-sided will be arcuate in shape. Such an arrangement is shown in Fig. 5 which represents a top-plan view of a platform I! the shaft ll of which is rotated by any suitable means, and this platform; carries at spaced intervals around its periphery a series of articles II to be subjected to the high frequency field. The iield coil I! is elongated and is similar to the coil of Fig. l with the exception that the main or body section of the convolutions is arcuate to correspond with the circumferential path travelled by the articles II as the platform rotates. In this embodiment of course, the ends of the coil II are oil'set vertically to enable the articles to enter and leave the field coil while the latter is stationary.

While certain specific embodiments have been disclosed and described herein, it will be understood that various changes and modifications may be made without departing from the spirit and scope oi the invention. For example, while the coil has been illustrated with both ends inclined or oflset with respect to the main body section, it will be understood that certain advantages of the invention may be obtained where only one end of the coil is oflset. Thus the entrance end of the coil may be oflset and the rest of the coil may be substantially fiat in which,

event the articles may be dropped off the conveyor before they engage the non-oilset end of the coil. Likewise, while the drawing shows the coil provided with the ends inclined at one particular angle, it will be understood that this inclination may be any angle desired consistent understood of course that the ends of each convolution are offset or bent upwardly inthe manner illustrated in Figs. 2 and 3.. However, in this embodiment, the convolutions I and III are ofiset inwardly with respect to the remaining convolutions so as to be in approximately the same coupling ratio with respect tothe reduced or neck section II of the charge I! as the coupling which exists between the remaining conwith the desired'sraduated heating eilect and with the necessary clearance at the entrance or exit ends as above described.

What I claim is:

i. A unitary field coil for induction heating lution being bent out 01 the plane 0! the convolution so as to enable the article to enter and leave the coil at opposite ends of the convolution, by a uni-directional motion with the coil ing at least one complete convolution having only the end sectionsbent at an angle to provide a graduated induction eifect at said end sections on a. charge moving at an angle to the convolution axis, and to provide at opposite ends a clear tion terminating in end sections, said end sections being inclined with respect to the main section to permit the charge moving at an angle to the axis of the convolutions to enter thecoil freely at one end, and to exit freely from the coil at the opposite end after passing between the side portions or said convolutions, without moving the coil, said end sections respectively being arched around the entering and exit paths.

4. A field coil for induction heating devices comprising a plurality of superposed helically wound elongated convolutions, the turns of the convolutions at one end being inclined with respect to the main body portion thereof and one or more turns of the main body section being of!- set inwardly to conform to the contour of an article to be passed through said coil for heating.

.5. An induction heating device comprising a platform for supporting articles to be heated, an induction field coil having atfieast one convolution with its magnetic axis extending toward the platform, said coil being stationary with respect to said platform, said platform being arranged a to carry said articles in succession through the space between the side portions of the turn or turns-of said coil to be enveloped by the field thereof, the end sections of said coi-l being offset to extend away from said platform to provide at one end of the coil a clear entrance path for-the entrance of the articles into the coil and at the opposite end a clear exit path for the articles,

' while the coil is stationary, and the sides of thecoil extending longitudinally of the path for the article with substantially uniform spaced relation to such path. a r

6. A field coil for induction heating compris ing a conductor having parallel elongated sides and inclined ends, said sides and ends constituting at least one continuous inductive loop, the said inclined ends providing for the article clear entrance and exit paths respectively at opposite ends of the coil while the coil is maintained stationary.

7. A unitary field coil for induction heating comprising a helically wound coil with the convolutions elongated in the direction of movement of a charge through the field thereof. the end sections being tilted to provide entrance and exit openings for the chargei said end sections respectiveiy being arched around the entering and exit paths.

supporting a series of articles to be heated, a pair of elongated conductor portions adapted to carry high frequency current and so arranged .in generally parallel spaced relation that such series of articles is enveloped by the field therebetween with close inductive relation between the articles and conductors, and other conductor portions at the ends or said first named portions and connected for substantially completing therewith an elongated convolution for forming a part of a high frequency circuit, said second named conductor portions at both ends of the convolution being. arched away from such close inductive relation to the articles at theends .of the convolution, to thereby somewhat reduce the effective strength of the field otherwise applicable to the articles at said ends.

9. In induction heating apparatus, means for supporting and conveying in succession along a predetermined path a series of articles to be heated, one or more pairs of elongated conductor portionsadapted to carry high frequency current and so arranged in generally parallel spaced relation that the series of articles is conveyed along therebetween in close inductive relation therewith, and other conductor portions at the ends of said first named portions and connected forsubstantially completing therewith one or more elongated loops for forming a part of a high frequency circuit, said second named conductor I portions extending from one side of said path generally transversely thereof around outside the path to the other side thereof while leaving the path unobstructed.

10. In induction heating apparatus, means for supporting and conveying in succession along a predetermined substantially arcuate path a series of articles to'be heated, one or more pairs of elongated correspondingly arcuate conductor portions adapted to carry high frequency current.

andso arranged in generally parallel spaced relation that the-series of articles is conveyed along therebetween in close inductive relation therewith, and other conductor portions at the ends of said first named portions and connected for substantially completing therewith one or more elongated loopsfor forming a part of a high frequency circuit, said second named conductor portions extending from one side of said path generally transversely thereof around outside the path to the other side thereof while leaving the path unobstructed.

EDWARD S. GOQDRIDGE.

8. In induction heating apparatus. means for 

